Electrical apparatus



June 6, 1961 G. G. DOUCETTE, JR

ELECTRICAL APPARATUS 2 Sheets-Sheet 1 Filed April 18, 1960 T n d June 6,1961 G. e. DOUCETTE, JR

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United States atent I 2,987,684 ELECTRICAL APPARATUS George G. Doucette,Jr., Pittsfield, Mass., assignor to General Electric Company, acorporation of New York Filed Apr. 18, 1960, Ser. No. 22,723 3 Claims.(Cl. 336-12) This invention relates to electrical apparatus and more inparticular to an improved winding for such apparatus.

Electrical induction apparatus such as transformers and the like areconventionally made with a low voltage winding surrounding a magneticcore and a high voltage winding surrounding the low voltage winding.Because the high voltage winding and low voltage winding are atdifferent potentials, they must be separated and insulated from eachother. In order to reduce the size and weight of such apparatus, it isdesirable that the gap separating the high voltage and low voltagewindings be kept to a minimum. Since the amount of insulation andspacing between the high voltage winding and low voltage winding is afunction of the potential diiference between these two windings, one wayof reducing the size of the gap is to arrange the windings in such amanner that the portions of the high and low voltage windings nearest toeach other are at the closest electrical potentials practicallyobtainable in the apparatus. While winding arrangements constructed inaccord with this principle have been proposed in the past, thesearrangements have not been satisfactory because they do not lendthemselves to mass production, assembly line techniques, and also theyhave required complicated channels for the flow of insulating andcooling fluid through the windings.

Accordingly, it is an object of my invention to provide an improvedwinding arrangement for electrical apparatus.

Another object of my invention is to provide an electrical transformerin which the spacing between high and low voltage windings is reduced toan acceptable minimum.

Other objects and advantages of my invention will become apparent fromthe following specification and the accompanying drawing.

Briefly stated, according to one aspect of my invention, the spacingbetween high voltage and low voltage layer windings is kept to anacceptable minimum by dividing some of the high voltage winding layersinto axially spaced sections that are connected in series so that thelayer closest to the low voltage winding is at the lowest practicalpotential. The turns of the closest layers of both high and low voltagewindings are contiguous and the ends of these layers are shielded. Thisconfiguration also provides continuous axial fluid flow channels throughthe windings.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

In the drawing:

FIG. 1 is a perspective partially cross-sectional view of an embodimentof electrical apparatus in accordance with my invention.

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is a schematic representation of the electrical winding of FIGS.1 and 2.

Referring to FIG. 1, therein is illustrated an embodiment of theteachings of my invention. An electrical transformer having a core 11with a plurality of legs 12 and electrical windings 13 around each legis disposed in a fluid-tight housing 14 in the well-known manner. Thetransformer may be provided with conventional accessories such asbushings, fluid expansion reservoirs, ex-

Patented June 6, 1961 ternal heat exchangers, etc., but such equipmenthas not been illustrated because it forms no part of the presentinvention.

In FIG. 2 the windings 13 are shown in greater detail. The windings 13each comprise a layer wound low voltage winding 20 and a layer woundhigh voltage winding 21. The windings are illustrated as being circular,but may assume other shapes without departing from the spirit of theinvention. The individual layers of the high voltage and low voltagewindings are spaced radially outwardly from each other in order toprovide continuous axial channels 22 for the flow of a cooling andinsulating fluid, such as transformer oil or a dielectric gas. Properspacing between the components of the winding may be obtained byattaching vertically extending spacers 15 to the insulation between thelayers. The low voltage winding 20 and high voltage winding 21 areseparated by a gap or space 23, the gap being provided with suitableinsulating material, such as layers of paper 24. The paper layers 24 mayalso be spaced radially from each other so as to provide axiallyextending fluid channels between the high and low voltage windings. Someof these channels may be blocked by barriers 42 to limit the flow offluid to those channels adjacent the windings.

Each layer of the low voltage winding 20 comprises a plurality ofaxially wound turns of an insulated electrical conductor 25. Theindividual layers may be insulated at the top and bottom by bands ofinsulating material 40, and separated by cylinders of insulatingmaterial 41. The turns of the radially outermost layer 26 of the lowvoltage winding are wound contiguous with each other in order tominimize stress concentrations that occur at the corners of each turn.Inner layers of the low voltage winding 20 may have the turns thereofspaced axially from each other at a central portion in order to axiallybalance the ampere-turns with those of spaced sections of the highvoltage winding 21.

In order to reduce the size of the gap 23 to an acceptable minimum andthus reduce the over-all size and Weight of the transformer Iii, thehigh voltage winding 21 has been made in accordance with the teachingsof my invention. By an acceptable minimum it is meant that the gap sizeis reduced to the smallest dimension at which the transformer 10 willpass the tests required by the trade to insure adequate safety factorsagainst insulation breakdown. Since the size or" the gap 23 is afunction of the potential diiierence between the radially outermostlayer 26 of the low voltage winding and the radially innermost layer 27of the high voltage winding, the size of the gap 23 can be reduced to anacceptable minimum if these layers are arranged so as to be at theclosest potentials practical. This can be accomplished by dividing someor all of the remaining high voltage winding layers into axially spacedwinding sections 29 and 29'. The sections 29 are connected in series,and the sections 29' are also connected in series. The respectivewinding sections 29 and 29' are also connected in series with theinnermost layer 27 at opposite ends thereof. When employing thisarrangement in delta connected apparatus, the leads 30 from the highvoltage Winding that are connected to the high voltage line are in theradially outermost winding layer and thus spaced the farthest distancefrom the low voltage winding. Consequently, the innermost high voltagewinding layer 27 is at the lowest practical potential for a fullyinsulated layer winding arrangement. An examination of the schematicillustration of this winding arrangement in FIG. 5 will reveal that theinnermost hi h voltage winding layer 27 is at roughly half the linepotential. The turns of the innermost layer 27 are contiguous for thesame reasons stated above with regard to the layer 26.

The respective axially spaced high voltage winding sections 29and'29 maybe effectively insulated 'from each other by bands or rings of solidinsulating material 32. The high voltage winding layers may beinsulated. at the top and bottom by bands of insulating material 40, andalso separated by cylinders of insulating material 41 and spacers 15.The exterior of the WindingIZ may beprovided with conventional lineshields 33. In order to eliminate stress concentrations at the ends ofthe high voltage and low voltage winding layers, each layer is providedwith conventional shield means 31 at its outer ends.

It will be apparent from inspection of the drawing that a winding madein accordance with the teachings of my invention can be fabricated inthe usual manner by winding the individual layers from separate lengthsof insulated conductor material 35 and then connecting the ends of theindividual conductors together by brazing. However, one of theadvantages of a winding in accordance with my invention is that it isreadily fabricated by mass production techniques. Once the fabricationof the winding 12 has been started by placing the insulating cylinder34- on a mandrel (not illustrated), the winding 12 need never be takenfrom the mandrel until it is completed because the successive windinglayers and insulation layers can easily be wound on top of each other.This eliminates the necessity of transporting partially fabricatedwindings from one place to another during the manufacturing operation.Thus, apparatus employing my improved electrical winding can be made bystandardized assembly line methods of production.

Although the invention has been described with reference to particularembodiments thereof, it will be understood that numerous modificationsmay be made by those Skilled in the art without actually departing fromthe scope of the invention. It is, therefore, intended that the appendedclaims cover all such equivalent variations as come within the truespirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Electrical apparatus comprising a magnetic core extending in an axialdirection, a low voltage winding comprising turns of an insulatedconductor wound axially in concentric radially spaced layers so as toprovide continuous axial fluid flow passages through the low voltagewinding, the turns in the layer of said low voltage winding spacedradially farthest from said core being contiguous, a high voltagewinding comprising turns of an insulated conductor wound axially inconcentric radially spaced layers so as to provide continuous axialfluid flow passages through the high voltage winding, there being aradial gap separating said high and low voltage windings, the turns inthe layer of said high voltage winding closest to said low voltagewinding being contiguous, other layers of said high voltage windingcomprising two winding sections separated axially from each other byinsulating means, radially adjacent layers in the respective highvoltage winding sections being serially connected so that the terminalends of the high voltage winding occur in the layer spaced radiallyfarthest from said low voltage winding, and means shielding the endturns of said closest high voltage Winding layer and said farthest lowvoltage winding layer, whereby the electrical stress across, and alsothe size of, the gap between said high and low voltage windings isreduced to an acceptable minimum.

2. Electrical apparatus comprising a magnetic core extending in an axialdirection, a low voltage winding comprising turns of'an' insulatedconductor'wound' axially in concentric radially spaced layers so as toprovide cotinuous axial fluid flow passages through the low voltagewinding, the turns in the layer of said low voltage winding spacedradially farthest from said core being contiguous, a high voltagewinding comprising turns of an insulated conductor wound axially inconcentric radially spaced layers so as to provide continuous axialfluid flow passages through the high voltage winding, there being aradial gap separating said high and low voltage windings, the turns inthe layer of said high voltage winding closest to said low voltagewinding being contiguous, the remaining layers of said high voltagewinding comprising two winding sections separated from each other insaid axial direction by solid rings of insulating material, radiallyadjacent layers in the respective high voltage winding sections beingserially connected so that the terminal ends of the highvoltage Windingoccur in the layer spaced radially farthest from said low voltagewinding, the turns in some of the low voltage winding layers beingaxially spaced to balance ampere-turns, and means shielding the turns atopposite ends of the high voltage and low voltage windings, whereby theelectrical stress across, and also the size of, the gap between saidhigh and low voltage windings is reduced to an acceptable minimum.

3. A fluid-cooled polyphase electrical transformer comprising anenclosure, a dielectric fluid in said enclosure, a magnetic core in saidenclosure, said core having a plurality of legs extending in an axialdirection, a low voltage winding around each core leg, each low voltagewinding comprising turns of an insulated conductor wound axially inconcentric radially spaced layers so as to provide continuous axialfluid flow passages through the low voltage winding, the turns in thelayer of each low voltage winding spaced radially farthest from saidcore being contiguous, a high voltage winding around each low voltagewinding comprising turns of an insulated conductor wound axially inconcentric radially spaced layers so as to provide continuous axialfluid flow passages through the high voltage windings, there being aradial gap separating each pair of high and low voltage windings, theturns in the layers of the high voltage windings closest to the lowvoltage windings being contiguous, the remaining layers of said highvoltage windings comprising two winding sections separated axially fromeach other by solid rings of insulating material, radially adjacentlayersin the respective high voltage *winding sections being seriallyconnected so that the terminal ends of the high voltage windings occurin the 'layers spaced radially farthest from said low voltage windings,the terminal ends of the respective high voltage windings being deltaconnected so that said closest layers are at approximately one-half ofline potential, the turns in some of the low voltage winding layers being axially spaced to balance ampere-turns, and means shielding theturns at opposite ends of each high voltage winding layer and each lowvoltage winding layer, whereby the electrical stress across, and alsothe size of, the gaps between said high and low voltage windings isreduced to an acceptable minimum.

References Cited in the file of this patent Hatfield Feb. 9, 1960

